Identification, expression pattern and functional characterization of As-MyD88 in bacteria challenge and during different developmental stages of Artemia sinica

• The myeloid differentiation factor 88 gene (As-MyD88) was cloned from A. sinica.
• As-MyD88 is vital to the immune response and dorsal–ventral axis formation.
• The As-MyD88 protein was mainly located in the head and chest of A. sinica.
• The expression level of As-MyD88 was high at early stage of embryo development.
• The expression level of As-MyD88 was high under bacterial infection.

Myeloid differentiation factor 88 (MYD88), a key adapter protein in Toll-like receptor signaling, affects the immune response and the formation of the dorsal–ventral axis. Here, the 1555bp full-length cDNA of MyD88 from Artemia sinica (As-MyD88) was obtained. Molecular characterization revealed that the sequence includes an 1182bp open reading frame encoding a predicted protein of 393 amino acids. The predicted protein contains a death domain in the N-terminus, and box1 and 2 motifs of the TIR domain in the C-terminus. Real-time quantitative PCR, Western blotting and immunohistochemistry were used to determine the expression level, protein production and location of As-MYD88 during embryonic development and bacterial challenge. The highest expression level during embryonic development was at the 0h and 5h stages of A. sinica. As-MYD88 was remarkably upregulated after bacterial challenge. Our results suggested that As-MYD88 plays a vital role in response to bacterial challenge, and during post-diapause embryonic development of A. sinica.